Nowadays, due to the deregulation of the Electricity Sector and in particular the deregulation of the medium voltage networks, the business of supplying electricity to customers over the medium voltage network is becoming more and more competitive. Providers of electricity are always looking for new ways to cut the costs of supplying the electricity to their customers. At the same time, the electricity providers are also being forced to provide a more reliable service to their customers with as few interruptions to the power supply as possible in order to satisfy their customer's demands as well as the demands of the Industry regulatory bodies.
In order to satisfy both of these requirements it has been found that by monitoring their networks more closely than ever before, the electricity providers may reduce the losses from the medium voltage network as well as being able to attend to any failures in the medium voltage network in as fast a manner as possible. This has been found to both reduce the overall cost of producing the electricity and to guarantee a faster response to any faults that may occur in the medium voltage network. There is a problem however with the known methods of monitoring the networks in that often the information provided by the measurement sensors will not be sufficiently accurate to give a true impression of what is actually happening on the medium voltage lines and it will have to await a fault condition in the line before any action is taken to rectify the problem.
Another problem with the known methods of monitoring the medium voltage network is that these methods only operate on overhead power lines. Nowadays, more and more of the power lines installed, particularly in and around cities, are subterranean lines and not overhead lines as was previously the case. The problem with subterranean power lines is that these lines experience a large capacitive current in the lines as compared to overhead lines. Therefore, when a line transitions from an overhead line to a subterranean line a significant change in the line condition occurs, this causes the known methods of monitoring the lines to produce erroneous measurements and results.
This is partly due to the manner in which the lines are being monitored, using sample by sample analysis of the lines. By using this technique, the methods are limited in the accuracy that they can achieve particularly when the lines contain subterranean portions. Therefore, the known methods are unsuitable for accurately measuring medium voltage networks in and around cities and other areas where a large portion of the medium voltage line is located underground.
Another problem with the known methods of monitoring the medium voltage networks is that the monitoring systems are purely reactive in that the systems always await a fault condition before taking any corrective action on the line. Quite often, this is in fact too late as the fault may be a significant fault resulting in a black out of power to an area which can greatly inconvenience the customers of the medium voltage network electricity supplier. This can result in the customers becoming dissatisfied with their electricity provider and looking for an alternative provider of their electricity needs. What is needed therefore is a method of monitoring the network that will allow for a more comprehensive analysis of the medium voltage network to be carried out which will permit a more proactive strategy to the monitoring and maintenance of the medium voltage lines. The monitoring will allow the electricity providers to carry out preventative maintenance on the power lines.
It is an object therefore of the present invention to provide a method of monitoring line faults in a medium voltage network that overcomes at least some of these difficulties and at the same time is cost efficient to implement.